1. Field of the Invention
The present invention relates to a method for manufacturing a magnetic recording medium including a recording layer formed in a concavo-convex pattern.
2. Description of the Related Art
Conventionally, in a magnetic recording medium such as a hard disc, areal density has been largely improved by various types of development such as miniaturization of magnetic particles forming a recording layer, change of the material for the recording layer, and miniaturization of head processing. The further improvement of the areal density continues to be expected.
However, many problems including the limitation of the head processing, erroneous writing of data on adjacent tracks caused by spreading magnetic fields of the recording head, crosstalk, and the like are made apparent. Thus, the improvement of the areal density by the conventional development approach has reached the limit. Therefore, as candidates of a magnetic recording medium that enables further improvement of the areal density, a magnetic recording medium such as a discrete track medium or a patterned medium, in which a recording layer is formed in a predetermined concavo-convex pattern, has been proposed (see Japanese Patent Laid-Open Publication No. Hei 9-97419, for example).
On the other hand, when the surface of the medium is formed in a concavo-convex pattern, the flying height of a head slider may be unstable, thus degrading the recording and reproduction characteristics. Therefore, it is necessary to flatten the surface of the medium by depositing a non-magnetic material over the recording layer of the concavo-convex pattern to fill concave portions and then removing the excess part of the non-magnetic material above the recording layer.
As a technique for processing a recording layer in a concavo-convex pattern, dry etching can be used. As a technique for depositing a non-magnetic material, a deposition technique used in the art of semiconductor manufacturing, such as sputtering, can be used. In addition, as a technique for removing the excess part of the non-magnetic material above the recording layer to flatten the surface, a process technique used in the art of semiconductor manufacturing, such as CMP (Chemical Mechanical Polishing), can be used.
However, CMP has the following problems. In order to remove slurry, cleaning and the like require large amount of time and cost. Moreover, because CMP is a wet process, when CMP is combined with a dry process such as a process for processing the recording layer, transfer of an object to be processed, and the like are complicated. This lowers efficiency of the whole manufacturing process. In other words, when CMP is used in the flattening process, the production efficiency is low.
In addition, in a case of performing CMP, it is not easy to control the processed amount and it is difficult to restrict end points (process end points) within a range of several nanometers. Therefore, the non-magnetic material may remain above the recording layer, or a part of the recording layer may be processed. This degrades the recording and reproduction characteristics.